Bottom-box score

The Bottom Box Score is the share of respondents who chose the worst (least favorable) option on a rating scale. It is used to see how many customers are clearly dissatisfied, even when the average rating looks fine.

For example, if 100 people answer "Rate our service from 1 to 5" and 8 pick 1 while 12 pick 2, the bottom box is 8% (just the 1s) or 20% (1 and 2 together, the bottom-2-box). The metric highlights the disappointed: those at risk of leaving, complaining, or posting negative reviews. A high bottom box signals problems even when the average is good. Linked to NPS and CSAT.

The Bottom Box answers "how many are furious or disappointed."

Definition

Bottom Box Score - the share of respondents who chose the worst (least favorable) answer option on a scale, out of the total number who answered. Formula: (number who picked the lowest option / total number of responses) x 100%. The opposite of the Top Box Score (the share of the highest ratings). The bottom box surfaces detractors, the dissatisfied, and those at risk of churn. It is used in satisfaction surveys, NPS, and service ratings. Linked to the Likert scale and rating scales.

In short: "what percentage gave the minimum" - a 1 out of 5, a 0-6 on NPS, "very dissatisfied".

Formula and examples

Bottom Box = (number who picked the worst option / total number of responses) x 100%.

1-5 scale. The bottom box is the share who picked 1 ("very poor"). The bottom-2-box is 1 and 2 combined.

NPS 0-10. On the NPS question, the bottom box is often taken as the share of detractors (0-6). NPS factors detractors in directly: promoters minus detractors. A high bottom box drags NPS down.

1-7 scale. The bottom box is just the 1. Or the bottom-2-box - 1 and 2.

Smileys (CSAT). "Very dissatisfied" is the bottom box. Visual scales are a topic of their own when you design satisfaction questions.

Bottom Box vs the average and Top Box

The average masks the problem. 90% fives and 10% ones gives an average of 4.6 - looks fine. But a bottom box of 10% means every tenth person is furious. They will leave, complain, and hurt your reputation.

Top Box is the share of enthusiasts. The bottom box is the share of the disappointed. The goal: a high top box and a low bottom box, ideally close to zero.

Why track the Bottom Box

Churn risk. Customers who give the minimum rating leave more often, cancel their subscription, and switch to competitors. The bottom box is an early indicator.

Negative reviews. Disappointed customers write reviews, complain on social media, and tell their friends.

Prioritization. The bottom box by department or touchpoint shows where problems concentrate. One store has a 3% bottom box, another 18%. Where do you act first?

Impact of actions. After making changes, check whether the bottom box dropped. A drop from 12% to 5% is a sign of successful improvements.

Common mistakes

Ignoring it when the average is "fine". An average of 4.2 is no reason to relax. A bottom box of 15% is a reason to sound the alarm.

Confusing the bottom box with NPS. NPS is a formula (promoters - detractors). The bottom box for NPS is the share of 0-6. They are related but not the same thing.

A small sample. On 30 responses, 2 ones is a 6.7% bottom box. That is random fluctuation. You need volume for a reliable estimate.

Not asking "why". The bottom box shows how many, not why. Add an open-ended question for those who picked the lowest options: "What could we improve?" - via logic jumps.

In SurveyNinja: how to calculate the Bottom Box

Create a survey with a scale question. SurveyNinja reports give you the distribution across the options. The bottom box = the share who picked the lowest option (or the two lowest). Response filters (Basic plan and above) give you the bottom box by department, period, or segment. Set up logic jumps: for everyone who picked 1 or 2, show an open-ended question, "What exactly did you dislike?". Hidden variables carry context - analyze where the dissatisfied customers are coming from.

The link to NPS and detractors

In NPS, detractors are those who scored 0-6. Their share is the bottom box for the NPS question. NPS = % of promoters (9-10) - % of detractors (0-6). A high bottom box directly lowers NPS. Working with the dissatisfied - a "why?" survey, a personalized response, fixing the issue - can reduce the bottom box and raise NPS. More on this in the NPS guide, and on how to respond to negative reviews.

Benchmarks and reference points

The lower the bottom box, the better. There is no universal threshold: norms depend on the industry, the scale and the question, so complex services such as telecom or utilities usually see more low ratings than premium retail. The most reliable reference is your own trend: rising is worse, falling is better.

How to reduce the Bottom Box

Identify the causes - a survey with an open-ended question for those who gave the lowest ratings. Segment - which touchpoint, product, or period drives the spike. React quickly - personal contact with the dissatisfied can turn them into loyal customers. Improve the pain points - if the bottom box is high after a support contact, improve support. Track - whether the bottom box fell after the changes. Linked to customer experience - the bottom box drops when the experience improves.

Example: Bottom Box in a call center

Suppose a call center runs a post-call survey, "Rate us 1-5". The average is 4.1 - normal. But the bottom box (a rating of 1) is 12%. Broken down by agent: three had a bottom box above 20%. It turned out the cause was difficult topics (returns, complaints) that the agents were not trained for. They trained them and added escalation. A quarter later the bottom box across the network was 5%, and 7% for the former laggards. The average barely changed (4.2), but the number of the furiously dissatisfied dropped more than twofold.

Bottom Box and Top Box together

Top Box is the share of enthusiasts, the bottom box is the share of the disappointed. Watch both metrics. A healthy picture: a high top box and a bottom box close to zero. An alarming one: a low top box and a high bottom box. A narrow average (everyone at 3-4) - low top, low bottom - is a "gray zone", neither delight nor fury. The goal is to shift toward the top box.

The link to feedback and reviews

Feedback from those who fall in the bottom box is gold. They tell you what is wrong. Do not miss it: set up a trigger - on a rating of 1-2, automatically offer an open-ended question or a contact with a manager. VOC (Voice of Customer) - bottom box respondents often give the most valuable insights. See the VOC entry on working with the voice of the customer.